Ballspline shaft with no ball retainer

ABSTRACT

A shaft assembly for transmitting a torque in a driveline system. The shaft assembly comprises an outer shaft member that extends along an axis and includes an interior surface defining a bore and a plurality of outer grooves at least partially delimiting the bore. An inner shaft member extends along the axis and includes an outer surface defining at least one of a plurality of inner pockets or a plurality of inner grooves aligned with the outer grooves. At least one rolling element is located between the outer grooves and the inner pockets or the outer grooves and the inner grooves. At least one of the outer surface of the inner shaft or the inner surface of the outer shaft is configured to axially retain the at least one rolling element and the shaft assembly does not include a ball retaining cage.

TECHNICAL FIELD

The invention generally relates to a shaft assembly for transmitting atorque. More specifically, the invention relates to a telescoping shaftassembly for transmitting torque in a driveline system.

BACKGROUND

A vehicle, such as a car, truck, sport utility vehicle, crossover,mini-van, marine craft, aircraft, all-terrain vehicle, recreationalvehicle, or other suitable vehicles, typically include a drivelinesystem for transferring power from an engine or other propulsion systemto the wheels. The driveline system generally includes a telescopingshaft assembly capable of transmitting a torque. The telescopic shaftassembly typically includes a tubular outer shaft member and an innershaft member. The inner shaft member is at least partially disposedwithin the outer shaft member and moveable relative thereto along alongitudinal axis. The telescopic shaft assembly typically uses rollingelements or bearings between the outer and inner shaft members to reducefriction during repeated telescopic compression and expansion.

The rolling elements of the telescopic shaft assembly are typicallyconfigured as steel rollers or steel balls. The rolling elements areconfigured to roll between the outer and inner shaft members duringlinear, telescopic movement of the telescopic shaft assembly whilerotational torque can continued to be transferred between the outershaft member and the inner shaft member.

A telescopic shaft configured to connect two constant-velocity joints isknown. This configuration typically includes a bearing retaining cagelocated between the outer and inner shaft that retains the rollingelements. The bearing retaining cage is typically located between theouter and inner shaft via holding elements. While telescopic shafts withbearing retaining cages are popular, they are not without shortcomings.For example, additional packaging space is typically required to locatethe ball retaining cage between the outer and inner shaft. The presenceof the ball retaining cage typically also results in a hydraulic-effectthat negatively impacts free relative telescopic movement.

Accordingly, there is a continuing desire to improve upon theoperational framework and efficiency of telescopic shafts in drivelinesystems to offer longevity of operational life, a reduction of thehydraulic-effect, a reduction in parts, and a reduction of packagingrequirements.

SUMMARY

This section provides a general summary of the disclosure and is not tobe interpreted as a complete and comprehensive listing of all of theobjects, aspects, features and advantages associated with the presentdisclosure.

This disclosure relates generally to a shaft assembly without a ballretaining cage that improves upon the operational framework oftelescopic shafts in driveline systems to offer longevity of operationallife, a reduction of the hydraulic-effect, a reduction in parts, and areduction of packaging requirements.

It is one aspect of the present disclosure to provide a shaft assemblyfor transmitting a torque. The shaft assembly comprises an outer shaftmember that extends along an axis and includes an interior surfacedefining a bore and a plurality of outer grooves at least partiallydelimiting the bore. An inner shaft member extends along the axis andincludes an outer surface defining at least one of a plurality of innerpockets or a plurality of inner grooves aligned with the outer grooves.At least one rolling element is located between the outer grooves andthe inner pockets or the outer grooves and the inner grooves. At leastone of the outer surface of the inner shaft or the inner surface of theouter shaft is configured to axially retain the at least one rollingelement and the shaft assembly does not include a cage.

It is another aspect of the present disclosure to provide a method ofassembling a shaft assembly for transmitting a torque. The methodcomprises providing an outer shaft member defining a bore, an innershaft member, and a sleeve. The method further comprises aligning afirst end of the sleeve with the bore and a second end of the sleevewith the inner shaft member. The sleeve includes a tapered section and astraight section. The method further comprises locating a first portionof the inner shaft member in the tapered section and placing a firstcircumferential array of rolling elements into one of inner pockets orinner grooves defined by an outer surface of the first portion of innershaft member. The method further comprises placing the first portion andthe first circumferential array of rolling elements past the taperedsection and into a straight section of the sleeve.

The foregoing has outlined rather broadly the features and technicaladvantages of the present invention in order that the detaileddescription of the invention that follows may be better understood.Additional features and advantages of the invention will be describedhereinafter that form the subject of the claims of the invention. Itshould be appreciated by those skilled in the art that the conceptionand the specific embodiments disclosed may be readily utilized as abasis for modifying or designing other embodiments for carrying out thesame purposes of the present invention. It should also be realized bythose skilled in the art that such equivalent embodiments do not departfrom the spirit and scope of the invention as set forth in the appendedclaims. These and other aspects of the present disclosure are disclosedin the following detailed description of the embodiments, the appendedclaims, and the accompanying figures.

BRIEF DESCRIPTION OF THE DRAWINGS

The disclosure is best understood from the following detaileddescription when read in conjunction with the accompanying drawings. Itis emphasized that, according to common practice, the various featuresof the drawings are not to-scale. On the contrary, the dimensions of thevarious features are arbitrarily expanded or reduced for clarity.

FIG. 1 is a perspective view of a shaft assembly including an innershaft member and an outer shaft member, wherein the outer shaft memberis illustrated as transparent to show features of the inner shaft memberaccording to the principles of the present disclosure.

FIG. 2 is a perspective view of the inner shaft member according to theprinciples of the present disclosure.

FIG. 3 is a perspective view of the outer shaft member according to theprinciples of the present disclosure.

FIG. 4 is a perspective view of another embodiment of a shaft assemblyaccording to the principles of the present disclosure.

FIG. 5 is a plan view illustrating sequential steps in a method ofassembling the shaft assembly according to the principles of the presentdisclosure.

FIG. 6 is a flow diagram generally illustrating the method of assemblingthe shaft assembly according to the principles of the presentdisclosure.

DETAILED DESCRIPTION

Example embodiments will now be described more fully with reference tothe accompanying drawings. In general, the subject disclosure isdirected to a telescoping shaft assembly for transmitting torque in adriveline system. However, the example embodiments are only provided sothat this disclosure will be thorough, and will fully convey the scopeto those who are skilled in the art. Numerous specific details are setforth such as examples of specific components, devices, and methods, toprovide a thorough understanding of embodiments of the presentdisclosure. It will be apparent to those skilled in the art thatspecific details need not be employed, that example embodiments may beembodied in many different forms and that neither should be construed tolimit the scope of the disclosure. In some example embodiments,well-known processes, well-known device structures, and well-knowntechnologies are not described in detail.

Referring to the Figures, wherein like numerals indicate correspondingparts throughout the views, a ballspline shaft with no ball retainer“shaft assembly” and a method of assembly is provided. The shaftassembly and method of assembly that improves upon the operationalframework of telescopic shafts in driveline systems to offer longevityof operational life, a reduction of the hydraulic-effect, a reduction inparts, and a reduction in packaging requirements.

Referring now to FIG. 1 , a shaft assembly is shown generally at 10. Theshaft assembly 10 is a rolling-element telescoping shaft assembly 10capable of connecting to or integrating with a driveline (not shown) andtransmitting a torque. Although the shaft assembly 10 may beincorporated into any suitable device, the shaft assembly 10 isparticularly suited for use as a telescopic shaft assembly in adriveline system of a vehicle such as an automobile. The shaft assembly10 includes an outer shaft member 12 and inner shaft member 14telescopically engaged with the outer shaft member 12. The outer shaftmember 12 extends along a longitudinal axis A and defines an innersurface 16, which defines an interior bore 18 centered on the axis A. Itshould be appreciated that a portion of the outer shaft member 12 thatdefines the bore 18 may be generally tubular. The inner shaft member 14is located within the bore 18 and moveable telescopically with respectto the outer shaft member 12. The inner surface 16 may include a ringgroove 17 (FIG. 2 ) for accommodating a snap ring 19 for retaining theinner shaft member 14 within the bore 18.

As best illustrated in FIG. 2 , the inner surface 16 of the outer shaftmember 12 defines at least one (e.g., a plurality of) outer grooves 20arranged in the inner surface 16. Each outer groove 20 extends along andmay be disposed generally parallel with the axis A. In some embodiments,each outer groove 20 may be circumferentially equidistant relative tothe axis A. In some embodiments, each outer groove 20 may be notcircumferentially equidistant relative to the axis A. As will bedescribed in greater detail below, each of the outer grooves 20 may beused to transmit torque to the inner shaft member 14 via one or morebearing elements 22 (FIG. 1 ) located therein. More particularly, aplurality of bearing elements 22 may be located in each of the outergrooves 20. In some embodiments, each outer groove 20 at least partiallyhouses the same number of bearing elements 22. The inner surface 16 mayfurther define at least one outer fluid groove 24 for reducing pressurebuild-up via the hydraulic-effect during operation. In some embodiments,the at least one outer fluid groove 24 includes an outer fluid groove 24next to one of the outer grooves 20. In some embodiments, the at leastone outer fluid groove 24 extends along the inner surface 16, parallelto the axis A, an equal or larger length than the outer grooves 20. Insome embodiments, the at least one outer fluid groove 24 has acircumferential width and a radial depth that are less than that of theouter grooves 20, for example, half the size or less than half the size.The outer fluid grooves 24 may be positioned symmetrically with respectto the axis A.

As best illustrated in FIG. 1 and FIG. 3 , the inner shaft member 14 isat least partially disposed within or enters the bore 18 of the outershaft member 12. The inner shaft member 14 defines an outer surface 26that extends and is telescopically moveable generally along thelongitudinal axis A when the shaft assembly 10 is assembled. The outersurface 26 of the inner shaft member 14 defines at least one (e.g., aplurality of) inner pockets 28 arranged in the outer surface 26. Eachinner pocket 28 may be configured as a partially sphere-shapeddepression (e.g., a hemisphere or less). Each inner pocket 28 may bedisposed in at least one line of pockets 29 that extends along the axisA and may be disposed generally parallel with the axis A. The at leastone line of pockets 29 may include a plurality of lines of pockets 29and each line of pockets 29 may be circumferentially aligned with one ofthe outer grooves 20. In some embodiments, each line of pockets 29 maybe circumferentially equidistant. In some embodiments, each line ofpockets 29 may be not circumferentially equidistant. An imaginary planedefined by an open end of each outer groove 20 may be positioned at animaginary plane defined by an open end of an inner pocket 28 in acorresponding line of pockets 29 such that corresponding outer grooves20 and inner pockets 28 generally mirror each other in circumferentialpositioning. Together, the corresponding outer grooves 20 and innerpockets 28 form respective bearing openings.

In some embodiments, each outer pocket 28 in a line of pockets 29 arespaced axially equidistantly. In some embodiments, the outer surface 26defines at least one inner fluid groove 30. In some embodiments, the atleast one inner fluid groove 30 includes an inner fluid groove 30between each of lines of pockets 29. In some embodiments, the at leastone inner fluid groove 30 extends along the outer surface 26, parallelto the axis A, an equal or larger length than the line of pockets 29. Insome embodiments, the at least one inner fluid groove 30 has acircumferential width and a radial depth that are less than that of theinner pockets 28, for example, half the size or less than half the size.The inner fluid grooves 30 may be positioned symmetrically with respectto the axis A and generally circumferentially aligned with the outerfluid grooves 24 with respect to the axis A. The inner pockets 28 mayhave a circumferential width and a radially depth that is generallyequal to that of the inner grooves 20. In some embodiments, the outergrooves 20 extend along the axis A a first distance and the lines ofinner pockets 29 extend along the axis A a second distance, wherein thefirst distance is greater than the second distance.

The shaft assembly 10 includes the plurality of rolling elements22—e.g., balls or rollers—each of which is rollingly arranged within acorresponding opening between the inner grooves 20 and the outer pockets28. The rolling elements 22 rollingly engage the outer shaft member 12and the inner shaft member 14 during relative axial motion between ortelescoping movement of the outer shaft member 12 and the inner shaftmember 14 with minimum sliding friction. The rolling elements 22 may beformed of stainless steel. In some embodiments, the rolling elements 22have a diameter and more than half of the diameter is located within theouter grooves 20 and the inner pockets 28. For example, because a cageis not needed, 95% or less, 85% or less, or 75% or less of the diameterof rolling elements 22 may be located within the outer grooves 20 andthe inner pockets 28. Moreover, the absence of the ball retaining cagecan further permit the shaft assembly 10 to have a smaller outerdiameter and a reduction in length as the ball retaining cage typicallyspaces the rolling elements 22 along the axis A.

A number of lines of pockets 29 can correspond to a number of outergrooves 20, wherein each of the inner pockets 28 in a line of pockets 29is arranged opposite to a corresponding outer groove 20 to form a pair.The number of pairs may be at least two, at least four, at least six, atleast eight, at least ten, or at least twelve. In this case, at leastone rolling element 22 is rollingly arranged between each inner pocket28 and the outer groove 28. A number of inner pockets 28 in each line ofpockets 29 may be equal. For example, the number of inner pockets 28 ineach line of pockets 29 may be at least two, at least four, at leastsix, at least eight, at least ten, or at least twelve. In theillustrated embodiment, the number of inner pockets 28 in each line ofpockets 29 may be nine.

Referring now to FIG. 4 , a shaft assembly 110 is shown in the assembledcondition in accordance with another embodiment. Unless otherwisestated, the shaft assembly 110 may share all the same features,elements, arrangements, compositions, and methods of assembly as thatpresented in FIGS. 1-3 . However, the inner pockets 28 are now replacedwith an inner groove 128. More particularly, the shaft assembly 110includes an outer shaft member 112 and inner shaft member 114telescopically engaged with the outer shaft member 112. The outer shaftmember 112 includes an inner surface 116 defining a bore 118. The innershaft member 114 is located within the bore 118 and moveabletelescopically with respect to the outer shaft member 112. The innersurface 116 of the outer shaft member 112 defines a set of outer grooves120 and a set of outer fluid grooves (not shown), which may beconfigured the same as those described in reference to FIGS. 1-3 . Theinner surface 116 may further include a ring groove 117 foraccommodating a snap ring 119 for retaining the inner shaft member 114within the bore 118.

The inner shaft member 114 defines an outer surface 126 that extends andis telescopically moveable generally along the longitudinal axis A whenthe shaft assembly 110 assembled. The outer surface 26 of the innershaft member 14 defines inner grooves 128 and inner fluid grooves (notshown). The inner grooves 128 may be located in general locationspreviously described in relation to the line of pockets 29 described inreference to FIGS. 1-3 . Moreover, each inner groove 128 may beconfigured to retain the same number of rolling elements 122 as the lineof pockets 29 previously described. In the illustrated embodiment, eachinner groove 128 holds eight rolling elements 122. Similar to theprevious embodiment, the shaft assembly 110 does not utilize a cage forretaining the rolling elements 122. As illustrated, each inner groove128 may extend between a first end 134 and a second end 136 and therolling elements 122 may extend substantially between the first end 134and the second end 136 and contact one another. The first end 134 andsecond end 136 may be partially sphere-shaped to abut a sphericalsurface of the rolling elements 122 and axially retain it therein. Insome embodiments, the rolling elements 122 have a diameter and more thanhalf of the diameter is located within the outer grooves 120 and theinner grooves 128. For example, because a cage is not needed, 95% orless, 85% or less, or 75% or less of the diameter of rolling elements122 may be located within the outer grooves 120 and the inner grooves128. In some embodiments, a diameter of the first end 134 and the secondend 136 is slightly larger than the diameter of the rolling elements122.

FIG. 5 is a plan view illustrating sequential steps in a method 200 ofassembling the shaft assembly according to the principles of the presentdisclosure. With initial reference to the leftmost drawing in FIG. 5 , asleeve 238 is located on an end of the outer shaft member 12, 112 thatdefines the bore 18, 118. The sleeve 238 includes an inner surface 240and defines a straight section 242 located next to the outer shaftmember 12, 112 and a tapered section 244 spaced from the outer shaftmember 12, 112 by the straight section 242. The inner surface 240 oftapered section 244 extends gradually radially outwardly in a directionaway from the straight section 242. A first portion next to a first end246 of the inner shaft member 14, 114 is placed within the taperedsection 244 and rolling elements 22, 122 are placed in a firstcircumferential array 248 in the inner pockets 28 or the inner groove128. The inner shaft member 14, 114 is then is moved deeper into thesleeve 238 such that the first circumferential array 248 is retainedagainst the inner surface 240 of the sleeve 238 and the first portion islocated in the straight section 242. In some embodiments, the innersurface 240 of the straight section 242 may define rolling elementretaining grooves 250 extending towards the outer shaft member 12, 112.Next, additional rolling elements 22, 122 are placed in a secondcircumferential array 252 in the inner pockets 28 or the inner groove128 located on a second portion of the inner shaft member 14, 114. Theprocess continues until each of the inner pockets 28 retain rollingelements 22, 122 or the inner groove 128 is filled with rolling elements22, 122 as described above. The snap ring 19, 119 is then placed withinthe ring groove 17, 117.

FIG. 6 is a flow diagram generally illustrating the method 200 ofassembling the shaft assembly according to the principles of the presentdisclosure. At 202, the method 200 includes providing an outer shaftmember defining a bore, an inner shaft member, and a sleeve. At 204, themethod continues by aligning a first end of the sleeve with the bore anda second end of the sleeve with the inner shaft member. In someembodiments, the second end of the sleeve defines a tapered section andthe first end of the sleeve defines a straight section. At 206, themethod continues by placing a first circumferential array of rollingelements into one of inner pockets or inner grooves defined by an outersurface of a first portion of the inner shaft member. At 208, the methodincludes moving the first portion of the inner shaft member further intothe sleeve (e.g., into the straight section). In some embodiments, theinner shaft member is moved from the tapered section towards a straightsection until the rolling elements are retained between one of innerpockets or inner grooves and an inner surface of the sleeve. At 210, themethod continues by placing additional circumferential arrays (e.g., asecond circumferential array) of rolling elements into one of innerpockets or inner grooves defined by another portion of the inner shaftmember (e.g., a second portion) and moving the inner shaft memberfurther into the sleeve. Step 210 repeats until all of the inner pocketscontain a rolling element or each of the inner grooves are filled torolling elements. Stated another way, at 210, the method repeats bothsteps 206 and 208 until all of the inner pockets contain a rollingelement or each of the inner grooves are filled to rolling elements. At212, the method continues by placing a snap ring between the outersurface of the inner shaft member and an inner surface of the outershaft member to retain the inner shaft member in the bore of the outershaft member.

While the invention has been described in detail in connection with onlya limited number of embodiments, it is to be readily understood that theinvention is not limited to such disclosed embodiments. Rather, theinvention can be modified to incorporate any number of variations,alterations, substitutions or equivalent arrangements not heretoforedescribed, but which are commensurate with the spirit and scope of theinvention. Additionally, while various embodiments of the invention havebeen described, it is to be understood that aspects of the invention mayinclude only some of the described embodiments. Moreover, any feature,element, or component of any one embodiment can be used in conjunctionwith any of the other embodiments. Accordingly, the invention is not tobe seen as limited by the foregoing description. On the contrary, thedisclosure is intended to cover various modifications and equivalentarrangements included within the scope of the appended claims, whichscope is to be accorded the broadest interpretation to encompass allsuch modifications and equivalent structure as is permitted under thelaw.

Claims what is claimed is:
 1. A shaft assembly for transmitting atorque, the shaft assembly comprising: an outer shaft member extendingalong an axis and including an interior surface defining a bore and aplurality of outer grooves at least partially delimiting the bore; aninner shaft member extending along the axis including an outer surfacedefining at least one of a plurality of inner pockets or a plurality ofinner grooves aligned with the outer grooves; at least one rollingelement located between the outer grooves and the inner pockets or theouter grooves and the inner grooves; and wherein at least one of theouter surface of the inner shaft or the inner surface of the outer shaftis configured to axially retain the at least one rolling element and theshaft assembly does not include a cage.
 2. The shaft assembly of claim1, wherein the outer surface of the inner shaft member defines the innerpockets and each of the inner pockets is sized to axially retain asingle rolling element.
 3. The shaft assembly of claim 2, wherein theinner pockets define a plurality of lines of pockets.
 4. The shaftassembly of claim 3, wherein each of the lines of pockets and each ofthe outer grooves are parallel to the axis.
 5. The shaft assembly ofclaim 4, wherein the outer grooves extend along the axis a firstdistance and the lines of pockets extend along the axis a seconddistance, wherein the first distance is greater than the seconddistance.
 6. The shaft assembly of claim 3, wherein the lines of pocketsand the outer grooves are disposed circumferentially around axis.
 7. Theshaft assembly of claim 1, wherein the outer surface of the inner shaftmember defines the inner grooves and each inner grooves extends betweena first end and a second end, wherein the at least one rolling elementincludes a plurality of rolling elements filling the inner groove tocapacity.
 8. The shaft assembly of claim 7, wherein the first end andthe second end of the inner grooves define a partial spherical shape. 9.The shaft assembly of claim 8, wherein each of the inner grooves andeach of the outer grooves are parallel to the axis.
 10. The shaftassembly of claim 9, wherein the outer grooves extend along the axis afirst distance and the inner grooves extend along the axis a seconddistance, wherein the first distance is greater than the seconddistance.
 11. The shaft assembly of claim 1, wherein the at least onerolling element has a diameter and more than half of the diameter islocated within the outer grooves and the inner pockets or the outergrooves and the inner grooves.
 12. The shaft assembly of claim 1,wherein the inner surface of the outer shaft member defines a pluralityof outer fluid grooves.
 13. The shaft assembly of claim 12, wherein theouter surface of the inner shaft member defines a plurality of innerfluid grooves.
 14. The shaft assembly of claim 13, wherein each of theouter fluid grooves are aligned with one of the inner fluid grooves. 15.The shaft assembly of claim 1, wherein the inner surface of the outershaft member defines a ring groove and a snap ring is located within thering groove to retain the inner shaft member in the bore of the outershaft member.
 16. A method of assembling a shaft assembly fortransmitting a torque, the method comprising: providing an outer shaftmember defining a bore, an inner shaft member, and a sleeve; aligning afirst end of the sleeve with the bore and a second end of the sleevewith the inner shaft member, the sleeve including a tapered section anda straight section; locating a first portion of the inner shaft memberin the tapered section and placing a first circumferential array ofrolling elements into one of inner pockets or inner grooves defined byan outer surface of the first portion of inner shaft member; and placingthe first portion and the first circumferential array of rollingelements past the tapered section and into a straight section of thesleeve.
 17. The method of claim 16, further including locating a secondportion of the inner shaft member in the tapered section and placing asecond circumferential array of rolling elements into one of innerpockets or inner grooves located on the second portion and placing thefirst portion into the straight section.
 18. The method of claim 17,further including placing a snap ring between the outer surface of theinner shaft member and an inner surface of the outer shaft member toretain the inner shaft member in the bore of the outer shaft member. 19.The method of claim 16, wherein the first circumferential array ofrolling elements is placed into inner pockets.
 20. The method of claim16, wherein the first circumferential array of rolling elements isplaced into inner grooves.